PedalScope · Part 4 · Reference

Advanced settings

The Advanced tab of Settings (⌘,) holds two sections, and the General tab holds the completion sounds (last on this page). They disclose tunable parameters that the app otherwise runs at fixed, documented values. Nothing there is required for normal use — the defaults are the standard the rest of this guide describes — but the parameters are real, so they are visible, editable where safe, and each group has its own Restore Defaults button.

Analysis — the sweep frequency range

New Harmonic Distortion and Gain Map runs sweep the range set here (standard: 20 Hz – 10 kHz). Two things to know before touching it:

  • Resolution comes from sweep duration, not the top frequency. The sweep spends its time in octaves; a longer sweep resolves more bass detail. Raising the top frequency buys almost nothing musical — near half the sample rate the measurement increasingly reflects the interface’s anti-alias filter and the pedal’s ultrasonic misbehavior (which the oscillation detector already flags) rather than tone.

  • Harmonics alias from the top down. A distortion pedal multiplies frequencies: harmonic k of a swept fundamental f lands at k·f, and once that passes half the sample rate it folds back corrupted. The app’s validity rules fade those reads and keep them out of every fit, summary, and comparison automatically — you cannot poison a stored number this way, but you can waste sweep time measuring nothing.

A non-standard range is honest by construction: every record stores the exact range it was swept with as part of its own payload, the Compare view flags a parameter mismatch between records measured differently, and the PSC-1 badge (see Comparing measurements) simply does not qualify a non-standard sweep — disclosure, not a defect.

Pluck synthesis — the Hear-it guitar

Why a synthesized note rather than a recording of a real guitar? Because every A/B in this app depends on the two sides differing only in the pedal: the renders are seeded and bit-exact, which is what lets a stored illustration be cached, hashed, and verified in CI, and what lets a level-stepped stimulus like the knee walk exist at all — a recorded phrase carries its own dynamics, and re-leveling one recorded pluck makes it quieter without making it softer, while the synthesis maps touch onto the excitation the way a hand does. A self-recorded library would also have to be recorded, rights-cleared, shipped inside the app, and level-matched by hand for every drive step. The string model costs none of that and answers to your ears here instead.

The synthesized plucks in the Hear-it panels come from an extended Karplus–Strong string model voiced as a DI electric guitar: a pluck-shaped excitation into a tuned, damped string loop — two of them, actually, weakly detuned like the two planes a real string vibrates in — heard through a pickup-position comb with a gentle pickup-loading rolloff. Seven of its parameters are adjustable:

  • Sustain multiplies each pluck’s decay time (its T60) — longer notes dwell in a pedal’s compression region, shorter ones emphasize the attack. Decay is compensated per note, so high notes and low notes ring for the same time.

  • Damping is the string loop’s lowpass cutoff in Hz — how fast the high harmonics die relative to the fundamental. 500 Hz is a dull muted string; 8–10 kHz a bright steel string.

  • Pick position sets where along the string the pluck strikes, as a fraction of the vibrating length — harmonics with a node at that point go missing, the comb character that voices the attack (0 disables it).

  • Pick cutoff is the excitation’s lowpass in Hz, from soft fingertip (≈ 2 kHz) to hard bright pick (≈ 7 kHz). Phrase stimuli map touch dynamics onto this automatically — a soft note is darker, not just quieter; setting it here overrides that mapping.

  • Burst length sets the noise burst’s length as a fraction of one string period — short is tight and percussive, a full period is the classic Karplus–Strong fill.

  • Polarization detune offsets the second string polarization (per-mille of the fundamental). The two polarizations decay at different rates, which is where the two-stage decay — fast drop, long quiet tail — and the slow beating of a held note come from (0 disables the second polarization).

  • Pickup position sets where along the string the pickup listens, again as a fraction of the vibrating length — the output comb that gives a DI electric its voicing (0 disables it).

Preview Pluck plays one synthesized pluck at the current slider positions — dry, with no pedal model in the way — so you can hear what each adjustment changes about the source itself before any Hear-it panel sends it through a measured pedal.

The preview, like every Hear-it panel, plays on your Mac’s default output. PedalScope chooses that device itself and checks that its audio engine is actually running on it before the first sample; if the engine cannot be started there — the default output has no output channels, or macOS moved the engine somewhere it cannot play — a line appears under the button naming the device and what did not happen, instead of a Play button that flicks and stays silent. The remedy is the one the line names: choose another output in System Settings → Sound and press Play again. Changing the default output while a Hear-it lane is playing moves the playback to the new device.

Factory positions are bit-identical to the shipped renders — leaving the section untouched changes nothing, not even a re-render. Custom settings re-render on demand, and every panel produced under them says custom pluck settings in its source label, so a tweaked illustration can never be mistaken for the documented default. Stored measurements and the guide’s own audio are never affected: these parameters shape only the illustrative audio synthesized at read time.

Completion sounds — the General tab

A family sweep is a hands-on-knobs task, and a long run is one you may walk away from. Settings → General → Play completion sounds (on by default) plays a short system alert sound on your Mac’s default output when a run settles, so you can turn away from the screen: one sound when a single measurement finishes, another when a Full Fingerprint finishes, a third — the most distinguishable, because it is the one that needs a hand — when a family run reaches its next prompt or its end, and a fourth when a measurement is aborted or fails. Each event has a picker over the system sounds (the same list System Settings → Sound offers) and a Play button to audition the choice; the four defaults are different sounds, so you can tell them apart without looking.

Two things the sounds never do. They never play during a capture: each one fires only after the measurement has finished and its record is saved (or the prompt is on screen), which is after the interface has stopped. And they never play into the measurement interface: nothing goes into the interface but the stimulus, so if your Mac’s default output is the interface itself (a one-interface bench, the pedal patched to its output), the sounds stay off and an orange line beside the toggle says so, naming the device — “Your default output is the Scarlett Solo USB, which is also the measurement interface, so completion sounds are off.” To have the sounds on such a bench, pick another default output in System Settings → Sound (the Mac’s own speakers, say); the line clears as soon as it changes. A scripted session started with --no-permission-prompts is silent too.